Hall: Guyton and Hall Textbook of Medical Physiology, 12th Edition
Chapter 07: Excitation of Skeletal Muscle: Neuromuscular Transmission and
Excitation-Contraction Coupling
Test Bank
1. A 45-year-old man has botulinum toxin (Botox®) injections in the frontalis muscles.
Which of the following sets of changes are most likely to occur in the treated muscles
with repeated injections over a period of ten years?
Fiber diameter Fiber number Contraction velocity
A. decreased decreased decreased
B. decreased decreased increased
C. decreased increased increased
D. increased decreased decreased
E. increased decreased increased
F. increased increased increased
2. Which of the following represents the correct temporal order of events for skeletal
muscle?
First Second Third
A. End plate potential Muscle action potential Nerve action potential
B. End plate potential Nerve action potential Muscle action potential
C. Muscle action potential End plate potential Nerve action potential
D. Muscle action potential Nerve action potential End plate potential
E. Nerve action potential End plate potential Muscle action potential
F. Nerve action potential Muscle action potential End plate potential
3. Myasthenia gravis is an autoimmune disease in which antibodies damage which of the
following?
A. Acetylcholine
B. Ligand-gated channels on postsynaptic membrane
C. Ligand-gated channels on presynaptic membrane
D. Voltage-gated channels on postsynaptic membrane
E. Voltage-gated channels on presynaptic membrane
4. Lambert-Eaton myasthenic syndrome is an autoimmune disease in which antibodies
damage which of the following?
A. Acetylcholine
B. Ligand-gated channels on postsynaptic membrane
Test Bank
7-2
C. Ligand-gated channels on presynaptic membrane
D. Voltage-gated channels on postsynaptic membrane
E. Voltage-gated channels on presynaptic membrane
5. A 59-year-old college professor visits his physician because of muscle fatigue that
worsens later in the day. The physician notices that the man has droopy eyelids and
seems to have an overall weakness in his muscles. After the intravenous administration of
Tensilon®, which blocks degradation of acetylcholine, the droopy eyelids and symptoms
of muscle weakness appear to subside. Which of the following best describes the
patient’s condition?
A. Encephalitis
B. Fibromyalgia
C. Flaccid paralysis
D. Myasthenia gravis
E. Poliomyelitis
6. A 3-year-old child is admitted to the emergency department of University Hospital. The
child exhibits extreme salivation, lacrimation, tremors, and tachycardia. The slight
erythema and mild edema found on the child’s hand suggest a spider bite. The mother
acknowledges that the child has a fascination with spiders and has seen black widow
spiders in the yard. The neurotoxic venom of the black widow spider (i.e., latrotoxin or
latrophilin) can increase the flux of calcium ions into the presynaptic terminal. What is
the likely outcome of a black widow spider bite?
A. Decreased acetylcholine release from nerve terminals
B. Hyperpolarization of postsynaptic membranes
C. Hyperpolarization of presynaptic membranes
D. Increased acetylcholine release from nerve terminals
E. Inhibition of acetylcholinesterase
7. An apparently healthy 12-year-old boy dies during a minor surgical procedure while
under general anesthesia. An uncle had also died during a surgical procedure. Results of a
halothane contracture test indicate that the child had malignant hyperthermia (MH). The
MH crisis is associated with which of the following?
A. Decreased anaerobic metabolism
B. Decreased CO2 production by muscles
C. Decreased lactic acid production by muscles
D. Defective ryanodine receptors
E. Decreased usage of ATP in muscles
8. Skeletal muscle and cardiac muscle contract when calcium binds to which structure or
molecule?
A. Active sites
B. Calmodulin
C. Myosin head
D. Tropomyosin
E. Troponin-C
9. Which of the following represents the correct temporal order of events for skeletal
muscle?
First Second Third
A. Muscle action potential Muscle contraction Nerve action potential
B. Muscle action potential Nerve action potential Muscle contraction
C. Muscle contraction Muscle action potential Nerve action potential
D. Muscle contraction Nerve action potential Muscle action potential
E. Nerve action potential Muscle action potential Muscle contraction
F. Nerve action potential Muscle contraction Muscle action potential
10. Binding of calcium to which structure or molecule initiates a contraction in smooth
muscle, skeletal muscle, and cardiac muscle?
Smooth muscle Skeletal muscle Cardiac muscle
A. Active sites Calmodulin Troponin
B. Active sites Troponin Calmodulin
C. Calmodulin Tropomyosin Active sites
D. Calmodulin Troponin Troponin
E. Myosin heads Tropomyosin Troponin
F. Myosin heads Troponin Tropomyosin
11. A 23-year-old man loses consciousness while driving, hits a tree, and dies within 15
minutes. The police find his stiff body five hours later. Rigor mortis is caused by a
decrease in which of the following?
A. Acetylcholine
B. Actin-myosin cross-bridges
C. Myoplasmic calcium levels
D. Interstitial lactate levels
E. Muscle ATP levels
12. A father and his 10-year-old daughter died suddenly of suffocation after ingesting
smoked whitefish chubs from the Great Lakes. Three other family members are sick,
complaining of dry mouths despite drinking copious amounts of fluids. Their upper
eyelids droop. Their vision is clear, but their pupils are wide and do not narrow when a
light is flashed. Two of them require artificial respiration. The suspect is botulism
(Clostridium botulinum). The surviving patients begin improving soon after receiving the
only treatment available, E antitoxin. The deadly effect of botulinum toxin results from
which of the following?
A. Decreased release of acetylcholine
B. Decreased release of norepinephrine
C. Depletion of muscle calcium stores
D. Skeletal muscle tetany
E. Stimulation of ryanodine receptors
13. Which of the following best describes the dynamics of calcium release and calcium
uptake during the development of frequency-induced muscle tetany?
A. Release from longitudinal tubules exceeds uptake by terminal cisternae
B. Release from longitudinal tubules exceeds uptake by T-tubules
C. Release from terminal cisternae exceeds uptake by longitudinal tubules
D. Release from terminal cisternae exceeds uptake by T-tubules
E. Release from T-tubules exceeds uptake by longitudinal tubules
F. Release from T-tubules exceeds uptake by terminal cisternae
14. Which of the following best describes the correct temporal order of events for the
opening of nicotinic acetylcholine (nACh) channels on the muscle membrane, the
opening of voltage-gated sodium channels on the muscle membrane, and initiation of
presynaptic action potentials (AP)?
First Second Third
A. nACh channels Presynaptic AP Voltage gated Na channels
B. nACh channels Voltage gated Na channels Presynaptic AP
C. Presynaptic AP nACh channels Voltage gated Na channels
D. Presynaptic AP Voltage gated Na channels nACh channels
E. Voltage gated Na channels nACh channels Presynaptic AP
F. Voltage gated Na channels nACh channels Presynaptic AP